Rheostat.



GI H. WHITTI NGHAM.

RHEOSTAT.

API LIOATION FILED MAR.19, 1909.

Patented NOV. 7, 191] wwwwoao GEORGE H. V]HITTINGHAM, OF BALTIMORE, MARYLAND, ASSIGNGR TO ll/EICFTILOR MAN- UFACTURING COMPANY OF BALTIMORE CITY, A CORPORATION 0 MM BHEOSTAT.

Application filed March 19, 1909.

T 0 all whom it may concern:

Be it known that I, Gannon H. VVHITTING- HAM, a citizen of the United States, residing at Balti1nore,'State of Maryland, have in vented certain new and useful Improve ments in Bheostats, of which the following is a specification.

My invention relates to controlling dcvices for electric circuits, and more particularly to a device in the nature of a manually operated rheostat.

In the control of electric motors, it is the common practice to insert a variable resistance o'r rheostat in the field or armature circuits, or both, so that, by properly manipulating such rheostats, any desired speed of the motor may be obtained. As usually constructed, such rheostats comprise a suit able panel, into which are set a series of pin: or buttons, between'which the coils of re sistance wire or ribbon are connected, and

a sweep arm pivotally mounted on said designates the usual panel, which may be -made of slate or other insulating material.

panel, and adapted to make contact with any one of said series of buttons, whereby more or less of the resistance may be included in the circuit. In certain classes of motor-driven apparatus, as, for example, printing presses, and some types oi" machine tools, it is highly desirable that the motor maintain a constant speed throughout the performance of any given piece of work, notwithstanding the fact that, during the required run, it may be necessary to frequently start and stop the motor. Since, where but a single rheostat is employed, a careless operator may fail to set the arm to the same point each time the motor is started, it has heretofore been proposed to employ two separate rheostats in connection with such motors, one being employed as a starting resistance, and the other, as a regulating resistance. Nith such an arrangement, the shop foreman may set the regulating rheostat to the desired point for the run, and the operator may then manipulate the other rheostat forj staring and stopping the motor, but without being able to afl'ect its speed when running. Trouble has been experienced, however, owing to the fact that unauthorized persons Wlll frequently change the position of the regulat- Specification of Letters Patent.

ing rheostat, after it has been properly setby the foreman, and thus deletericusly affeet the quality of the work turned out.

It is the primary object of the present inl Contact pins or buttons connected the resistance coils 3, convention- Fatented Nov. 7,19i3i.

Serial No. 5284,567.

vention, therefore, to provide a rheostat having an arm which may be positively locked in any desired positlon, i hereby the shifting of such arm. by unau1i1xrized persons, may be effectively prevented.

A further object of the invention is to provide a rheostat of this character which shall be simple in design, efficient in action, and easy to produce and operate.

\Vith the above objects in view, and to improve generally upon the details of such apparatus, my invention consists in the construction and. arrangement of parts hereinafter described, and illustrated in the accompanying drawings, in which Figure l is a front view of my improved rheostat' complete; Fig. 2 is a perspective view of the controlling arm; Fig. 3 is a central section through. the controlling arm and part of the panel; and, Fig. 4 is a sec-1 .tional view of the spring latch.

Referring to the drawings in detail, 1

In this panel is arc shaped series of 52, between which are ally shown. in'dotted lines in 1. At each side of the contact buttons is also mounted a stop pin l, to limit the movement of the arm. The controlling arm itself comprises ,a frame or body portion 5, having at one end a journal 6, adapted to cooperate with a pin 7, set into the panel 1 The arm may be retained in position on the pin 7 as by means of a cotter pin 8 or other suitable fastening device. At the other end of the arm is the usual operating handle 9.

Carried by the arm is a latch comprising a head 10, and a shank 11, as clearly shown in Figs. 3 and 4c. The outer end of the latch is V-shaped, as shown in Figs. 1 and i, and is adapted to engage any one of the pins 2. The beadlO of the latch is divided by a. horizoi'itally extending slot 13, in which works a pin 14, supported in a pair of brackets 15, projecting downwardly from the body of the arm. The lugs 15 are spaced apart a distance equal to the width of the latch head, and are of a length approxi mately' the same as the thickness of the head 10. A third lug 16, arranged near the inner end of the arm on the under side thereof, is provided with an. opening adapt ed'tc receive the end of the shank 11. A

coil spring 17 surrounds the shank l1, and in confined between the head 10 and the lug 16. It will thus be seen that this spring serves to maintain the latch in the position. shown in Fig. 3, with the beveled face 12 thereof in contactwith one of the pins 2. It'will, therefore, be observed that, in operation, the current passes from the pin 7, through the body of the arm to the latch head 10, and thence by way of the V-shaped faces 12 of the latch, into the sides of the pins'2. Where the current is heavy, a flexible cable (not shown) may be soldered or otherwise secured to the arm and the latch, so as to form a low resistance connection.

With the arrangement so far described, it will be seen, that as the arm is moved about the pivot pin 7 the beveled faces 12 of the latch will ride up the side of one pin and down the side of the next, thus snapping from pin to 'in as the arm is moved, and always held in close engagement with the pins by means of the spring 17. It will be observed that when the V-shaped end of the latch is in engagement with any pin, as shown in Fig. 1, the arm will be resiliently held in position so that it is not likely to become accidentally displaced.

Carried by the arm 5, and preferably formed integral therewith, is a casing 18 adapted to receive a lock of any suitable type. This lock is clearly shown at 19, in-

Fig. 3, and is provided witha key-hole 21, which is accessible through an opening 20 formed in the front of the casin 18. The lock 19 may conveniently be of the type usually employed by cabinet makers, and is provided with a reciprocatin bolt 22. As shown in Fig. 3, the bolt 22 s projected to its fullest extent, and, when retracted, it retreats entirely into the lock casing'lQ; so that its end is flush with the sides thereof. From a further inspection of Fig. 3, it will be eyident'that when the bolt is projected, as shown, it lies directly in the path of the latch head 10, and consequently .when the bolt is in this position, the latch will be prevented from moving inwardly away from the pins 2. If, therefore, when the arm is in some such position as indicated in Fig. 1, the bolt 22 be projected by turning the key 23 in the lock, the latch 10 will be rigidly locked in posit-ion and, owing to the engagement of the V-shaped latch end with the pin 2, it will be impossible to move the arm 5 in either direction. When, on the other hand, the bolt is retracted, an. ample space will be provided in which the latch head 10 may freely reciprocate, and hence the cam faces 12 may readily be forced to rise over the pins, as above described, and the arm moved to any desired osition.

It will, therefore, e apparent, that by means of the above construction, a shop foreman, for example, may set his regulating rheostat at any point which he may desire and, having set it in the proper position,

may positively lock the arm in such position.

He may then withdraw the key from the lock, and consequently, during his absence,

it will be impossible for any unauthorizedthereby advantages of my invention will be readily appreciated by those skilled in the art.

\Vhat I claim is 1. In a rheostat, a panel having a series of projections thereon, a contact member mounted on the panel and movable parallel with the surface thereof, a spring-pressed latch on said member adapted to engage said' pI'OJGCtlOIIS successively as the member is moved, and locking means, including a removable key, for locking said latch in engagemcnt with any desired projection of the series.

2. In a rheostat, an arm therefor, a series of buttons with which said arm is adapted to contact, and means for rigidly locking ,said arm in contact with any desired button,

such locking. means engaging the button itself.

3. In a rheostat, an arm therefor, a series of contact buttons cooperating therewith, a spring latch carried by said arm and adapted to snap from one button to another as the arm is moved, and means for locking said latch against movement.

4. In a'rheostat, an arc-shaped series of contact pins, an arm concentrically mounted with respect thereto, and a lock carried by said arm and co-acting with the sides of said pins and serving, when operated, to rigidly hold said arm in any desired position.

5. In a rheostat, an arc-shaped series of contact pins, an arm concentrically mounted with respect thereto, and a spring latch carried by said'arm and adapted to engage the sides of said pins, said latch snapping from one pin to the next as thearm is moved, and. serving to yieldingly maintain said arm in position.

6. In a rheostat, an arc-shaped series of contact pins, an arm concentrically mounted in respect thereto, and a spring-prcssed latch carriedby said arm and adapted to engage the sides 'of said pins, said latch snapping fromone pin to the next as the arm is moved, and means for locking said latch a ainst movement when desired, whereby sai arm is rigidly held in position.

7. In a rheostat, an arc-shaped series of contact pins, an arm concentrically mounted with respect thereto, a latch carried by said arm and having a V-sha ed end adapted to engage said pins, means or resiliently holding said latch in contact with one of said an arc-shaped series of projections, a springpins, and means for rigidly locking said latch adapted to engage said projections and latch against movement away from said snap from one to the other as the arm is pin, when desired, whereby movement of moved, and a lock for preventing movement 15 5 the arm is prevented. of said latch when deslred.

8. In a rheostat, a pivoted arm therefor, In testimony whereofI afiix my signature, an arc-shaped series of projections, a lock in presence of two witnesses.

cooperating with said projections to hold GEORGE H.- WHIITINGHAM. the arm in any desired position, and a re Witnesses: v 0 movable key for said 100 FELIX R. SULLIVA1- I,

9. In a rheostat, a 'pivoted arm therefor, A. JARIUS. 

